Mimm 465: Lecture 24 Streptococci

Front 1

What kind of bacteria are Streptococci? (main characteristics)

Back 1

G+
Non-motile
Non spore forming
Cocci
Facultative anaerobes

Front 2

What morphology do they take when plated?

Back 2

Pairs/chains

Front 3

What kind of pathogens are they considered to be?

Back 3

Extracellular

Front 4

What is a good test to differentiate Strep from Staph?

Back 4

Catalase

Front 5

Are strep catalase + or -?

Back 5

Catalase -

Front 6

How do strep divide?

Back 6

Cell wall stretched between different cells in the chain
Can clearly see the septum
They divide in a single plane (this is how you get chains)

Front 7

What are the dif types of hemolysis on blood agar?

Back 7

a-hemolytic
B-hemolytic
y-hemolytic

Front 8

Describe a-hemolysis.

Back 8

INCOMPLETE hemolysis of RBCs surrounding the colony
Green color

Front 9

What is an example of an a-hemolytic strep?

Back 9

S. pneumoniae

Front 10

Describe B-hemolysis

Back 10

COMPLETE hemolysis of RBCs around the colony
Clear appearance

Front 11

What are the toxins responsible for hemolysis in Strept

Back 11

Streptolysin S (GAS)
B-hemolysin (GBS)

Front 12

What is an example of a GAS that uses Streptolysin S?

Back 12

S. pyogenes

Front 13

What is an example of a GBS that uses B-hemolysin?

Back 13

S. agalactiae

Front 14

What is y-hemolysis?

Back 14

NO hemolysis

Front 15

Identification scheme:
Test to differentiate btw Strept and Staph

Back 15

Catalase test
Strep: Negative
Staph: Positive

Front 16

Identification scheme:
Test to differentiate btw S. aureus and S. epidermidis

Back 16

Coagulase test:
S. aureus: +
S. epidermidis: -

Front 17

Identification scheme:
Test to differentiate btw different strep

Back 17

Hemolysis on blood agar
a-hemolytic: S. pneumonia
B-hemolytic: GAS, GBS
y-hemolytic: other strep and enterococci

Front 18

What is serological typing of GAS based on?

Back 18

M ptn (cell surface ptn)

Front 19

How many known M ptns have been identified?

Back 19

86

Front 20

What are some serotypes of GAS ass't with (pathogenically)?

Back 20

Throat infection
Skin tropism

Front 21

What has serotyping been replaced with?

Back 21

Sequence typing of the 5' end of teh M ptn (emm) gene

Front 22

How many emm types have been identified so far?

Back 22

190 emm types

Front 23

What is an example of a GAS?

Back 23

Strep pyogenes

Front 24

What does S. pyogenes do?

Back 24

Widespread disease in humans

Front 25

What are the mild infections S. pyogenes can cause?

Back 25

*Pharyngitis (strep throat)*
Impetigo (skin infections
Scarlet fever (scarlatine)

Front 26

What are the severe infections that S. pyogenes can cause?

Back 26

*Necrotizing facilities (flesh eater, outbreak in Canada in the 1990s)
Sepsis
Streptococcal Toxic Shock Syndrome (STSS)

Front 27

What can happen to patients following an acute GAS infections?

Back 27

Can develop immune mediated disease:
Acute rheumatic fever (swelling of the heart)
Glomerulonephritis (damage to the kidney)

Front 28

What is the mortality rate for patients with STSS?

Back 28

35%
->Necrotic factor
(mortality of all inasive cases is 10-15%)

Front 29

How many T serotypes are there?

Back 29

20 (comes from the T Ag)

Front 30

What is a noninvasive GAS infection?
How many ppl are affected by this/year?

Back 30

Throat/skin infection
over 10 million ppl affected

Front 31

What is an example of a GBS?

Back 31

S. agalactiae

Front 32

Where is S. agalactiae commonly found?

Back 32

GIT
Genital tract

Front 33

What is S. agalacitae the leading cause of?

Back 33

Septicemia
Meningitis
Pneumonia in newborns (transmission from mother to child during delivery)
Becoming more of a problem for immunocompromised adults

Front 34

What is the mortality for neonatal GBS infections?

Back 34

5-10%

Front 35

How many capsular serotypes does S. agalaciae have?

Back 35

9
Ia, Ib, II-VIII

Front 36

What is the genome size of a GAS?

Back 36

1,900,000 bp (very small)
1,7 Mbp is conserved btw all serotypes
~2000 ORFS

Front 37

How many serotypes of S. pyogenes have been sequenced?

Back 37

13
(M1, M3,M5, M18, M28 etc)

Front 38

What disease is M28 closely ass't with?

Back 38

Neonatal sepsis (child-bed fever, which is usually caused by GBS)

Front 39

Which region is shared among GBS strains and M28 GAS strains?

Back 39

37 kb region of difference 2 (RD2)

Front 40

Where does S. pneumoniae reside in the human?

Back 40

Naso-pharynx
Part of the microflora

Front 41

What diseases does S. pneumoniae cause?

Back 41

**Leading cause of pneumoniae in elderly ppl
A;so causes: otis media, meningitis and sepsis

Front 42

What's one of the problems ass't with S. pneumoniae?

Back 42

Resistant to many antibiotics

Front 43

How many capsular serotypes does S. pneumoniae have?

Back 43

85

Front 44

What does the strep pneumoniae vaccine consist of?

Back 44

Mix of 23 most common capsular serotypes
Efficacy is controversial

Front 45

What are some species of the viridans gp streptococci?

Back 45

S. gordonii
S. mitis
S. mutans
S. sanguis

Front 46

In what part of the body are the viridans gp part of the normal microflora?

Back 46

Oral cavity

Front 47

What % of bacteria in the oral cavity are strep?

Back 47

80%

Front 48

Where do strep bind in the oral cavity? How?

Back 48

Bind enamel coated with salivary ptns (primary colonizers)
They also coaggregate

Front 49

Why is S. mutans responsible for dental caries?

Back 49

Its acidogenic and acidophillic

Front 50

What happens if the Viridans gp bacteria gets released into the bloodstream (through tooth extraction or periodontitis)?

Back 50

Can cause infective endocarditis

Front 51

Are most viridans pathogenic?

Back 51

No most aren't except S. mutans
MOst will only cause pathology if they reach the blood

Front 52

Where do strep bind in the oral cavity?

Back 52

Don't bind enamel directly
Bind to ptn of saliva that binds to enamel

Front 53

What kind of a virulence factor is the M protein?

Back 53

Multifunctional (major) virulence factor of GAS

Front 54

What encodes the M ptn?

Back 54

emm gene

Front 55

What is the M ptn virulence factor involved in?

Back 55

Adhesion
Internalization into host cells
Inflammation
Has antiphagocytic properties

Front 56

Through what mechanism are some serotypes associated with acute rheumatic fever?

Back 56

Molecular mimicry

Front 57

How is M ptn anchored to the cell wall?

Back 57

Sortase: Srt A

Front 58

Describe M ptn

Back 58

Extends to cell surface as an alpha-helical coiled-coil dimer
N-terminal HYPERVARIABLE region has serotype-specific aa sequence (M1, M2 ...)
N-terminal regions bind fibrinogen and complement ptns

Front 59

What are serotypes M1 and M3 associateed with?

Back 59

Serious infections"
Necrotizing fasciitis
STSS

Front 60

What is the difference btw a M1 isolate responsible for pharyngitis and a M1 isolate responsible for invasive disease?

Back 60

7bp frameshift mutation in covS gene

Front 61

What does the CovR/CovS 2 component system do?

Back 61

up/downregulates transcription of 15% og the genes

Front 62

What happens to the GAS when there is this 7bp frameshift mutation?

Back 62

Go from noninvasive to invasive disease

Front 63

Describe this transition from mucosal to invasive disease

Back 63

1) GAS confronted by the NETS (neutrophil extracellular traps) of neutrophils when it reaches the subcutaneous tissue. The SpeB factor degrades virulence factors and diminishes invasiveness
2) Mutations in CovR/S TCS causes lower production of SpeB and higher production of GAS DNase that degrades teh NETs
3) Pathogen survival increases
4) Enhanced probability of invasive infection

Front 64

Look at figure bottom page 9

Back 64

look at figure bottom page 9

Front 65

What are the various strep virulence factors responsible for? What does it cause?

Back 65

Adherence
Internalization
Invasion
Anti-phagocytic activity
=> Causes: Systemic toxicity and dissemination

Front 66

What pathway does streptokinase activate in humans?

Back 66

Fibrinolytic path
Converts plasminogen into plasmin, without proteolytic cleavage

Front 67

What are GBS80 and GBS104?

Back 67

Surface Ag
Confer protection vs GBS infection in mouse model

Front 68

What happens when e- microscopy was done of GBS80 or 104?

Back 68

Pilus-like structures extending from the bacterial surface were revealed

Front 69

What motif do both GBS80 and GBS104 have?

Back 69

LPXTG motif (that is found in surface ptn attched to the cell wall p/g)

Front 70

Describe pilus assembly in GBS

Back 70

Tip ptn is one minor subunit (GBS52 or GBS104)
Shaft ptn is the major subunit (GBS80)
Pip sortase corresponds to SrtC, which attaches pili
SrtA is the housekeeping sortase, attaches to many things

Front 71

What do cell wall glycopolymers (CWGs) include?

Back 71

Teichoic acids attached to the cell wall (WTA)
Lipoteichoic acids attached to glycolipids (LTAs)

Front 72

What role do CWGs have?

Back 72

Protective role
Attachment and colonization
-> LTA binds to fibronectin
Role in Innate immune system: activates TLR2 and mediates resistance to AMPs

Front 73

Describe lipoteichoic acid (LTA)?

Back 73

Glycolipid anchor
repeating units of 1,3-glycerol-phosphate (~40units)

Front 74

What can replace th eglycerol gps of LTA?

Back 74

D-alanine, though ester bonds
Requires DltA, B, C, D that are encoded in an operon

Front 75

What does the PO4- gp on LTA confer?

Back 75

Polyanionic properties
Expose NH2, which is positively charged. PO4- neutralizes it
->Partial neutralizing is achieved by modifying the polymer with D-alanine

Front 76

What happens if the dltABCD operon on LTA is disrupted?

Back 76

Increased net negative chare on the bacterial surface
->This results in INCREASED Susceptibility to AMPs

Front 77

What does incorportaion of D-alanine into teichoic acids contribute to?

Back 77

AMP resistance
GAS pathogenesis

Front 78

Describe the transfer of L-Lys to p/g

Back 78

Phosphatidylglycerol (PG) is negatively charged and favors interactions with +vely charged AMPs
MprF modifies PG by adding L-lys, making lysyl-phospohatidylglycerol (L-PG)
L-PG is +vely charged
->Results in repulsion of AMPs
Lysine gp is most likely derived from lysyl-tRNA

Front 79

How are AMPs sensed?

Back 79

2 component system in the bacteria

Front 80

What do AMPs trigger?

Back 80

Adaptive response in the host

Front 81

What hapens once AMPs activate the 2 component system?

Back 81

Activate dlt operon
Activate mprF gene
Increased export of of AMPs out of the bact cell, through ABC transporters

Front 82

What does LTA of GAS bind?

Back 82

Fibronectin

Front 83

What is the binding important for?

Back 83

LTA= "First step" adhesin
Brings GAS in contact with host cells

Front 84

How many adhesins with the LPXTG motif (other than LTA) recognize different host receptors?

Back 84

15

Front 85

What are the 5 different fibronectin binding ptns, that mediate adhesion to both skin cells and respiratory epithelial cells?

Back 85

Sfbl (streptococcal fribronectin binding ptn I)
SfbII
Fibronectin binding ptn 54
Ptn F2
PFBP

Front 86

What does the capsule of S. pyogenes consist of?

Back 86

Hyaluronic acid (HA)

Front 87

Describe HA (hyaluronic acid)

Back 87

Linear polysac composed of repeating, negatively charged disac unit of glucuronic acid and N-acetylglucosamine

Front 88

Where else is HA also found?

Back 88

Host connective tissue

Front 89

What does it mean that hyaluronic acid (HA) is in the host as well?

Back 89

It is non-antigenic

Front 90

What is the HA capsule essential for?

Back 90

Resisstance to phagocytosis

Front 91

What are some exported ptns of strep?

Back 91

Pore forming tocins
Superantigens
Proteolytic enzymes
DNases

Front 92

What are the pore-forming toxins?

Back 92

Streptolysin O (SLO)
Streptolysin S (SLS)

Front 93

What are some superAg?

Back 93

SpeA
SpeC
SpeG
SpeH
SpeJ
SpeK
SSA
SMEZ
SMEZ-2

Front 94

What are examples of proteolytic enz?

Back 94

Cysteine proteases SpeB and IdeS
ScpC
Scpa

Front 95

What do proteolytic enx do?

Back 95

SpeB, IdeS: Cleave human IgGa
ScpC: cleaves CSC chemokine IL-8
ScpA: celaved chemoattractant C5a

Front 96

What are DNases important for?

Back 96

Avoid trapping by neutrophil extracellular traps (NETs)